Metal polishing apparatus



Dec. 8, 1970 F. Housi'oN 3,545,133

METAL POLISHING APPARATUS. 1

Filed June 17 1968 I NVENTOR Z;%W, ZW

United States Patent 3,545,138 METAL POLISHING APPARATUS Russell F.Houston, Hamilton, Ohio, assignor to The Mosler Safe Company, Hamilton,Ohio, a corporation of New York Filed June 17, 1968, Ser. No. 737,431

Int. Cl. B24b 7/00 US. Cl. 51-59 8 Claims ABSTRACT OF THE DISCLOSUREMethod and apparatus for finishing a metal surface so as to obtain ametallic satin grain finish consisting of numerous parallel striations.This finish is achieved by grinding the metal surface with a coarsegrain abrasive so as to achieve a striated surface having numerousparallel short bright striations. The surface is then polished by aunique reciprocating band polisher in which the abrasive band is backedby a resilient element and is regularly indexed during the polishingoperation. This polishing then converts the short bright striationsproduced during grinding to long dull or satin striations having a woodgrain type of appearance.

This invention relates to the finishing of metal surfaces and moreparticularly, to an apparatus for achieving a satin or dull wood graintype of finish on a metal surface without the application of any paintor decorative material to the surface of the metal.

'In many applications metal surfaces must be finished or polished insuch a manner that the surface is decorative but still gives theimpression of being an exposed unpainted, unplated, or artificiallycolored metal surface. One such application is that of metal safes,vaults, and safety deposit boxes where the exposed metal surface conveysthe impression of impenetrability. Because of this impression, banks andsavings institutions often insist that the exterior of vaults, safes andsafety boxes be decorative but still have the appearance of an exposedmetal surface.

Another criteria of any metal surface finish applied to the exterior ofbank vaults or safes is that the finish be capable of duplication orrefinishing in the field since no finish will remain perfect forever.

One finish which has satisfied all of these criteriabeauty, metallicappearance, and capability of duplication in the field-has been adecorative striated grain finish. This finish is now commonly applied tothe exposed surfaces of vault doors, safes or safety deposit boxes byfirst grinding the surface and then manually hand-polishing it with anabrasive belt.

Grinding of the surface is accomplished with a coarse abrasive beltgrinder, as for example an abrasive belt having an aluminum oxideabrasive of a grit size from a number 60 to 120. At the end of thisgrinding operation, the surface has a rough ground surface appearance,i.e., the appearance of short bright parallel striations in the surfaceof the metal. Traditionally, this surface is then finished byhand-rubbing it with a polishing emery cloth wrapped around acylindrical rubber tube. At the end of the polishing operation, thesurface has asatin or dull type of wood grain finish consisting ofnumerous parallel long striations. Because the polishing is donemanually in the factory, it may be easily repaired in the field byduplicating the polishing operation there.

The only disadvantage of this finishing technique is that it isextremely expensive to apply because of all of the manual laborinvolved. It is also difficult to maintain uniformity because ofoperator fatigue, differences in strength of different operators, anddilferences in pressure applied in a single stroke. Furthermore, the

Patented Dec. 8, 1970 length of a stroke is limited to the reach of anoperators arms so that awkward setups are required on long parts.

It has been a primary objective of this invention to determine someapparatus for mechanically duplicating the grained finish which hasheretofore only been produceable manually.

This invention is predicated upon the discovery that an attractivegrained finish may be mechanically produced if the metal is first groundwith a rough abrasive and then polished by reciprocating a narrowsection of abrasive cloth over the ground surface and indexing the clothregularly so that the section of cloth which is engaged with theworkpiece surface remains in contact with the surface such a short timethat it cannot become loaded with workpiece chips.

We have found that conventional sanding machines Will not give thedesired efiect but will produce a surface finish that closely resemblesa ground finish, i.e., numerous short bright striations in the workpiecerather than a long striation, dull or satin type grained structure. Wehave further found that the desired finish may be produced on areciprocating sander type of machine if the machine is modified so thata rubber or resilient roller serves as the backing for the abrasivematerial and the emery cloth or abrasive material is regularly indexedso that a new section of emery cloth is regularly moved beneath theroller.

This machine has the advantage of eliminating a great deal of handworkwhich has heretofore been required to produce a highly decorativegrained finish on metal. Additionally, it produces a superior finish inthat the finish is more uniform than has heretofore been capable ofproduction on a manual basis. -It also eliminates the necessity forawkward fixtures to enable manual operators to have access to largesurfaces. And most importantly, it is capable of manual repair andduplication in the field.

These and other objects and advantages of this invention will be morereadily apparent from the following description of the drawings inwhich:

FIG. 1 is a diagrammatic illustration of a reciprocating sanding machineequipped with the invention of this application,

FIG. 2 is an enlarged front elevational view of the reciprocating headof the machine,

FIG. 3 is a cross sectional view through the reciprocating heat taken online 33 of FIG. 2, and

FIG. 4 is an end elevational view of the ratcheting mechanism of thereciprocating head.

Referring to FIG. 1, there is illustrated a reciprocating sander type ofmachine 10 commonly used in the woodworking industry but modified with aunique reciprocating head 12 to enable the machine to be used in thepractice of this invention. This machine comprises a fixed frame 11, avertically adjustable table 13, and a transversely movable feed slide.14. Workpieces 15 to be finished on the machine are clamped on theslide 14 by conventional C clamps, magnetic clamps, or any otherconventional form of clamping mechanism.

In the practice of this invention, workpieces 15 are first ground toprepare the top surface 16 to receive the grain finish imparted by themachine 10. This grinding operation is preferably performed on aconventional belt grinder such as a Hammond Flat Finishing Machinemanufactured by Hammond Machinery Builders, Inc., of Kalamazoo, Mich. Analuminum oxide abrasive belt of from 60 to 120 grit size is preferablyused for this grinding operation and produces a surface having asmoothness which measures approximately 70 to millionths of an inch rootmeans square. The abrasive material may vary, and the grit or grain sizemay vary slightly from this range, depending upon the composition of themetal, its surface treatment and hardness, and the exact grain structuredesired in the finished product. Additionally, if the surface is roughor imperfect, the surface may first be ground in a rough grind operationto remove surface imperfections. This pre-grind operation may beaccomplished with any type of grinder and a rough abrasive of from 36 to60 grit size. Ordinarily, the rough grind will producev a surface havinga measured smoothness of approximately 300 to 350 millionths of an inchroot mean square.

Throughout this application, abrasives are described in terms of theircomposition and grit size. As is conventional in the abrasive industry,grit size refers to the mesh of a screen through which the abrasivegrains will pass before being stopped in the next smaller mesh screen.For example, a sixty (60) grit size abrasive is one in which the grainsof abrasive material pass through a 60 mesh (openings per square inch)screen before being stopped in the next smaller standard mesh screen.

Finish polishing or so-called strip scouring of the workpiece is thenperformed in the belt sanding machine 10. One suitable machine useful inthe practice of this invention is a Curtis Belt Sander manufactured bythe Curtis Machine Company of Niagara Falls, N.Y. This sander comprisesa vertically movable table 13 having a transversely movable feed slide14 mounted thereon. An overhead beam 17 of the frame supports thereciprocal sanding head 12, the reciprocation of which is controlled bytwo motors 18 and 19 located at opposite ends of the beam and operativeto drive an endless cable 20 in reciprocation. When the head .12 isclamped to this cable, it is caused to reciprocate with the cable overan inverted T-shaped beam 21. As the head is reciprocated, the feedslide 14 moves the workpiece rearwardly into and beneath the beam 17 sothat the complete top surface 16 of the workpiece is exposed to thebottom surface of an abrasive belt 22.

The conventional reciprocating head 12 comprises a central body orcasting 24 having front and rear caps 25, 26 bolted thereto. This body24 and the caps 25, 26 support a pair of upper front rollers 27, 28, apair of upper rear rollers 29--29, a pair of lower front rollers 30, 31,and a pair of lower rear rollers 32-32. All of these rollers arerotatably supported upon stub shafts 35 mounted within the body 24 andare rollable over horizontal flanges 36, 37 of the beam 21. To preventlateral movement of the body relative to the rail, front and rearrollers 33, 34 are engageable with and movable over vertical edges 38,39 of the flanges 36, 37 of the rail 21.

The reciprocating sanding machine heretofore described is conventionalin the woodworking art and has therefore not been described in detailherein. To practice the invention of this application, the head '12 has,however, been modified by the addition of a unique abrasive belt support40 as described more fully hereinafter.

The support 40 comprises a supporting plate 42 which depends from aT-shaped slide 43. The slide 43 is adjustably mounted within a T-shapedslideway 44 in a bottom depending section 45 of the body 24 and may belocked therein by a set screw (not shown).

Four vertical studs 47 extend through unthreaded apertures in the fourcorners of the plate 42 and are threaded into apertures in a base plate48. A pair of washers 49, 50 and a compression spring 51 are mountedover each of the studs 47 above the upper plate 42. These washers 49, 50are biased apart by the compression spring 51 and, upon properadjustment, function to maintain the depending base plate 48 in ahorizontal plane.

A ball bearing 55 is mounted between the plates 42, 48 and is supportedin a recess 52 in the bottom of the plate 42 and a recess 53 in the topof the plate 48. This ball bearing 55 holds these plates 42, 48 inspaced relationship while still permitting the lower plate 48 to rockabout the bearing against the bias of the springs 51.

A semi-cylindrical roll 56 of neoprene rubber is secured to the bottomof the base plate 48. This roll preferably has a hardness ofapproximately 90 durometer and serves as a resilient backing for theabrasive belt 22.

Base plate 48 has four lateral braces 57-57, 58--58 extending upwardlyand outwardly from the four corners thereof. These braces are all boltedto the front and rear side edges of the base plate 48 by screws 59. Twoof these braces 58-58 rotatably support a storage roll 60 of theabrasive belt 22 while the two others 5757 rotatably support a takeuproll 6.1 therebetween.

As may be seen most clearly in FIGS. 2 and 4, a generally L-shapedoutboard brace 65 is bolted to the outer end of one brace 57. One leg 66of this brace 65 has a ratchet supporting bracket 67 fixedly securedthereto and a threaded stop 69 is adjustably mounted in the other leg68.

To effect rotation of the takeup roll 61, a conventional ratchet 70 ofthe type which may be purchased in any hardware store as a part of a setof socket wrenches is rotatably mounted between a setscrew 71 and thefront side wall 72 of the brace 57. The setscrew 71 is adjustable withina threaded aperture 73 in the bracket 67 and may be locked in anadjusted position by a lock nut 74. As may be seen most clearly in FIG.4, the takeup roll 61 has a journal pin press fit into one end. Thisjournal pin 80 extends into an aperture 81 of the brace 57 and rotatablysupports the roller 61.

The journal pin 80 has a square aperture 82 machined in one end andadapted to receive the square-ended drive shaft 83 of the ratchet 70.This driving relationship between the ratchet shaft 83 and the journalpin 80 enables oscillatory arcuate movement of the ratchet 70 to impartrotational movement to the takeup roll or drum 61.

A pair of ratchet actuating arms 86, 87 are bolted to the handle '88 ofthe ratchet 70 and support a dowel pin 89 therebetween. This dowel pin89 is engageable with a cam stop 90 (FIG. 1) attached to the frame 17 ofthe machine so as to effect oscillatory movement of the outer end 88 ofthe ratchet 70 upon engagement of the pin 89 with the cam stop 90. Tobias the ratchet in a clockwise direction as viewed in FIG. 2, a tensionspring 85 is at tached at one and 84 to the arm 86 and at the oppositeend to leg '68 of the outboard brace 65.

In operation, a workpiece is first prepared for polishing or forapplication of a striated grain finish by grinding the surface 16 with abelt grinder. The belt should have an abrasive of from 60 to 120 gritsize. Depending upon the condition of the surface and imperfectionstherein, a rough grind or pre-grind operation may be required to removerecesses, holes, etc., from the surface of the workpiece. Ordinarily,this pre-grind operation is accomplished with an aluminum oxide abrasivehaving an abrasive grain size of from 36 to 60 grit and produces asurface finish in the general range of 300- to 350 root mean square.

After the grinding operation is completed, the surface 16 has a roughstriated finish consisting of numerous parallel short bright marks. Theroughness of the surface should be between 60 and 80 millionths of aninch root mean square as measured by a conventional surface roughnessmeasuring instrument.

After grinding, the workpiece is clamped to the top surface of the table13 with the previously ground surface 16 in the uppermost position andin a horizontal plane. The table 13 is then moved upwardly until the topsurface of the workpiece 16 is engaged with the abrasive belt 22 whichextends from the storage roll, over one end of the base plate 48,beneath the contact roll 56, over the opposite end 97 of the base plateand into engagement with the takeup roll 61. The end of the belt 22 maybe secured to the takeup roll in any way desired, as for example byfitting the end of the belt into a radial slot of the roll or by tapingthe belt to the peripheral surface of the roll. The workpiece surface ismoved upwardly into engagement with the belt 22 until the band ofcontact A between the top surface 16 of the workpiece and the abrasivebelt is approximately one-half inch in width.

The abrasive belt 22 is either an aluminum oxide abrassive or a siliconcarbide abrasive belt having a cloth or paper backing. The abrasive hasa grain size of from approximately '80 to 120 grit. In one preferredembodiment, the surface is just polished with a belt 22 having a grainsize of 80 grit and is then finish polished with a belt 22 having anabrasive grain size of 120 grit. After both polishing operations, thecompleted surface has a surface smoothness of approximately 40 to 60millionths of an inch, root mean square.

After mounting of the workpiece on the table 13, the head 12 of themachine is then reciprocated by the drive motors 18 and 19 of themachine while simultaneously the feed slide 14 of the table 13 is fedinwardly so as to expose the complete surface 16 of the workpiece to thebelt 22 of abrasive material.

Referring to FIG. 1, it will be seen that as the head 12 reaches theleftward extent of its travel and passes off of the left edge of theworkpiece, its direction of movement is reversed and it returns to theright until it passes off of the right edge of the workpiece. The dowelpin *89 attached to the upper end of the ratchet arm 88 then engages thecam stop 90 causing the upper end of the ratchet arm to be moved to theleft so as to rotate the takeup roll 61 and pull a new section of belt22 into the operating band A. The linear travel of the belt 22 over theroll 56 is preferably one-half inch, the same as the width of the band Aso that a new section of abrasive is moved into the band A after theband has moved completely across the width of the workpiece twice, onceas the head moves leftward and once as it moves rightward.

After indexing movement of the ratchet 70in a counterclockwise directionas viewed in FIG. 2, the head 12 reverses its movement and moves to theleft while the outer end of the ratchet arm moves in a clockwisedirection into engagement with the end 98 of the adjustable stop screw69. The screw should be positioned so that the ratchet effectsapproximately one-half inch of travel of the band 22 each time theratchet arm engages the cam stop 90.

In making only two passes over the top surface of the workpiece beforethe belt is indexed, the operative band A of abrasive belt engaged withthe workpiece does not have sufiicient exposure to the workpiece surfacefor the abrasive grains to become broken and smooth or for the abrasivebelt to become loaded with chips or swarf. Consequently, the abrasivebelt 22 imparts a dull satin finish of from 40 to 60 millionths of aninch root mean square smoothness to the workpiece. This finish ischaracterized by long parallel striations or lines which give theappearance of a grain type of finish. This is a highly desirable finishbecause of its decorative characteristics and its repairability in theevent that it becomes scarred or damaged in the field. If it is damaged,it may be repaired by a workman rubbing a rubber cylinder covere by anabrasive belt over the damaged surface. After a few passes of the beltover the surface, the damaged surface will once again perfectly matchthe surrounding area.

While I have described only a single preferred embodiment of myinvention, those persons skilled in the arts to which this inventionpertains will readily appreciate numerous changes and modificationswhich may be made without departing from the spirit of my invention.Therefore, I do not intend to be limited except by the scope of thefollowing appended claims.

Having described my invention I claim:

1. Apparatus for polishing a flat surface of a metal article to obtain agrain type of finish consisting of numerous long parallel striations,said apparatus comprising:

means for supporting said article,

a polishing head including a long narrow resilient pad mounted on thebottom of said polishing head, the narrow dimension of said padextending transversely to said head, means for supporting a long widestrip of abrasive material on said head, which strip passes beneath saidresilient pad, said strip of material having abrasive of between andgrit size secured thereto,

means for effecting relative longitudinal reciprocating movement betweensaid polishing head and said workpiece while a narrow section of saidabrasive strip of material on said head is engaged with said flatsurface of said article, that section of said strip which is engagedwith said surface being backed by said resilient pad, and

means for repeatedly and regularly indexing said strip on said head soas to place an unused section of said strip in engagement with saidsurface before a portion in engagement with said surface can becomeloaded with chips.

2. Apparatus for polishing a fiat surface of a metal article to obtain awood grain type of finish consisting of numerous long parallelstriations, said apparatus comprising:

means for supporting said article,

a polishing head including a long narrow resilient pad mounted on thebottom of said polishing head, means for supporting a long wide strip ofabrasive material which passes beneath said resilient pad,

means for effecting relative longitudinal reciprocating movement betweensaid polishing head and said article while a section of said abrasivestrip of material on said head is engaged with said fiat surface of saidarticle, that section of said strip which is engaged with said surfacebeing backed by said resilient pad, and

means for repeatedly and regularly indexing said strip on said headduring reciprocation of said head so as to place an unused section ofsaid strip in engagement with said surface before a portion inengagement with said surface can become loaded with chips.

3. The apparatus of claim 2 wherein said indexing means includes aratcheting mechanism.

4. Apparatus for polishing a flat surface of a metal article to obtain awood grain type of finish consisting of numerous long parallelstriations, said apparatus comprising:

a frame including an overhead beam,

a polishing head mounted for longitudinal reciprocating movement uponsaid beam, said polishing head including a long narrow resilient padmounted on its bottom side, the narrow dimensions of said pad extendingtransversely to said head, a storage roll rotatably mounted upon oneside of said head and a takeup roll rotatably mounted on the oppositeside of said head, a long wide band of abrasive material etxending fromsaid said storage roll beneath said resilient pad and over to saidtakeup roll,

means including a table for supporting a metal article having a flatupper surface beneath said polishing head,

means for effecting relative longitudinal reciprocating movement betweensaid polishing head and said article while that section of said abrasiveband beneath said resilient pad is engaged with the top surface of saidarticle, and

means for intermittently and regularly indexing said band of abrasive onsaid head during reciprocation of said head so as to place an unusedsection of said band in engagement with said surface before a portion inengagement with said surface can become loaded with chips.

5. The apparatus of claim 4 wherein said indexing means includes aratcheting mechanism operative to pcriodically index said takeup roll.

6. The apparatus of claim 5 wherein said ratcheting mechanism isengageable with a stop at one end of the reciprocating movement of saidpolishing head over said beam.

7. The apparatus of claim 2 wherein said apparatus pivotal support, saidhead including resilient means for comprises a frame including anoverhead beam for supbiasing said body to a position in which the bottomsurporting said polishing head for longitudinal reciprocating face ofsaid resilient pad is located in a horizontal plane. movement over saidarticle supporting means, said article supporting means including atable having a flat upper 5 References Cited h 1 b d h 11 UNITED STATESPATENTS sai po1s mg ea mcu inga o y avingagenera y flat bottom surface,said head including a storage g u roll rotatably mounted upon one sideof said body 6 8 4 6 4 9/ 928 Yummer and a takeup roll longitudinallyspaced from said 10 A coung 5 T storage roll and rotatably mounted onthe opposite 16 OX 9 side of Said body and 2,284,556 5/1942 Brackett51-59 3,416,261 12/1968 Sherman et al. 51--60 a long strip of abrasivematerial extending from said storage roll longitudinally beneath saidresilient pad LESTER M SWINGLE Primary Examiner and over to said takeuproll. 15

8. The apparatus of claim 7 wherein said body is US. Cl. X.R.

mounted for universal pivotal movement about a central 5l36l Patent No.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Inventor(s) R. F.HOuStOn Dated December 8, 1970 It is certified that error appears in theabove-identified patent 2, line 47,

the

2, line 70, the

4, line .42,

the

5, line 56,

I Attesting Officer the word

word

word

word

and that said Letters Patent are hereby corrected as shown below:

"heat" should be head "means" should be mea'n "and" (before the figure84) should "covere" should be covered :sxawanm swan W9 87! m1. mum,mnion or Paton

